Transactions with Affiliates - Schedule of Amounts Charged to UTSI (Detail) - Affiliates [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	$ 20,548	$ 19,477	$ 55,326	$ 60,107
Administrative support services [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	615	572	2,346	1,702
Truck fuel, tolls and maintenance [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	29	645	910	1,912
Real estate rent and related costs [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	3,418	4,230	10,999	12,947
Insurance, bonds and employee benefit plans [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	16,394	14,010	39,907	43,511
Purchased transportation and equipment rent [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	$ 92	$ 20	$ 1,164	$ 35